X-Ray Scattering Studies of the Melting of Lead Surfaces

We report x-ray scattering studies of liquid layers on the Pb (110) and (111) surfaces at temperatures substantially below the bulk melting point of Pb. Surprisingly, the initial liquid scattering appears at $\approx 220 \mathrm{K}\mathrm{or}<\frac{1}{2}{T}_m$ on both the (110) and the (111) surfaces. On the (110) surface, analysis of the scattered intensity yields 2-3 monolayers of liquid from 575 to 599 K while substantially less than 1 monolayer of liquid is present on the (111) surface.